The Manchester United manager, Sir Alex Ferguson, can eventually see Major League Soccer being made up of four conferences, such are the rapid advances being made by football in the United States.

Ferguson's first experience of US football was the now-defunct North American Soccer League, which was filled with overseas signings such as Pelé, Johan Cruyff and George Best.

Even eight years ago, when United embarked on their first commercial tour, opposition was drawn from Europe and Mexico to ensure the standard was high enough to generate public interest.

Now, though, Ferguson knows his team face tough examinations even though three of United's five matches this summer involve teams drawn from the domestic league, with a fourth featuring an MLS All-Star team containing David Beckham, Thierry Henry and Landon Donovan.

In two years' time, the MLS will confirm a 19th franchise, which is tipped to mark the return of the legendary New York Cosmos.

"I always thought the problem would be the size of the country," Ferguson said ahead of Wednesday's game with the New England Revolution. "Travelling from Boston to Los Angeles is a long haul.

"But in Brazil they have two leagues. They could easily do that in the United States if it takes off and they got more clubs involved. In fact, you could have four leagues because of the size of the country and the population base. There are unbelievable possibilities for the United States."

Over 50,000 fans are expected at the Gillette Stadium to watch the Champions League runners-up. That is three times the normal number of supporters who would be expected to attend an MLS game. Nevertheless, it is a significant portion of a city which boasts top NBA, MLB and NFL teams.

"It is different to when I first came here in 1978," Ferguson said. "I went to see quite a few teams to see if I could bring something to Aberdeen that would have been useful in terms of not just the football side but the commercial side. But it was difficult. Teams used to travel to play three away games at a time and it never really worked.

"Now we see the United States in a different light. There is evidence now that they are starting to produce their own players. They have advanced their game because of the coaching and their sports science. That has put them to a different level in terms of my appreciation of them and also my understanding that you are not going to get an easy game."